Prior to approval for medical use in the United States, all pharmaceutical agents are subjected to rigorous testing for efficacy and safety. Typically, methods of assessing the efficacy of a pharmaceutical agent include complex studies of pooled patient samples or pooled data, and statistical interpretation of the results. The conclusions that follow such studies are inherently generalized or averaged over the subject patient population. With pharmaceutical agents, however, and particularly with cancer chemotherapeutic agents, the efficacy of an agent in treating an individual patient can vary greatly from the generalized data, often to the detriment of the individual patient. The need has long been recognized for a method of assessing the therapeutic potential of pharmaceutical agents, including but not limited to chemotherapeutic agents, for their specific efficacy in an individual patient.
Assays exist which expose malignant tissue of various types to pharmaceutically-active agents for the purpose of assessing the best choice for therapeutic administration. For example, in Kruczynski, A., et al., “Evidence of a direct relationship between the increase in the in vitro passage number of human non-small-cell lung cancer primocultures and their chemosensitivity,” Anticancer Research, vol. 13, no. 2, pp. 507-513 (1993), chemosensitivity of non-small-cell lung cancers was investigated in in vivo grafts, in in vitro primocultures, and in commercially available cancer cell lines. The increase in chemosensitivity was documented and correlated with morphological changes in the cells in question. Often, animal model malignant cells and/or established cell cultures are tested with prospective therapy agents, see for example Arnold, J. T., “Evaluation of chemopreventive agents in different mechanistic classes using a rat tracheal epithelial cell culture transformation assay,” Cancer Res., vol. 55, no. 3, pp. 537-543 (1995).
According to prior art methods of using specific patient tumor cells to form an in vitro assay particular to that patient, the cells are harvested (biopsied) and trypsinized (connective tissue digested with the enzyme trypsin) to yield a cell suspension suitable for conversion to the desired tissue culture form. The in vitro tissue culture cell preparations which result from these prior art methods typically fail to accurately replicate the chemosensitivity of the original tumor or other cell biopsy. This inability arises, in part, because the heterogeneity of cell population in the tumor tissue has been disturbed in culture, or entirely obliterated such that the cell culture preparation is essentially monoclonal. Moreover, prior art methods of culturing actual patient tissue samples inevitably result in cell cultures with a significant level of non-target cells, such as fibroblasts or other stromal cells, which have a tendency to outgrow the target tumor cells in a cell culture. Furthermore, standard cloning and tissue culture techniques are complicated and expensive for use in individualized patient testing. Thus, a need remains for improved and efficient methods of cell culture preparation that provide a heterogeneous cell population that substantially comprises target cells from a particular patient. Such a cell culture preparation is useful in drug or chemotherapeutic agent screening to provide information indicative of the in vivo reactivity of the cells, and thus the specific efficacy as to a particular patient.